Nonwoven fabrics and methods of making and using same

ABSTRACT

Substantially compostable nonwoven fabrics comprising staple fibers made from natural cellulosic fibers optionally mixed with other natural, man-made or synthetic fibers are described. Also described are methods of preparing such nonwoven fabrics that can include the steps of at least one of needle punching and/or hydroentangling and optionally resin bonding and/or thermal bonding. The compostable, or substantially compostable nonwoven fabrics disclosed herein provide improved durability over conventional nonwoven fabrics.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority to U.S. Provisional Application 62/410,060, filed Oct. 19, 2016, which is incorporated by reference herein in its entirety.

FIELD

The subject matter disclosed herein relates to nonwoven fabrics that are durable and substantially compostable and/or biodegradable.

BACKGROUND

Conventional nonwoven fabrics made from entangled staple fibers (short fibers normally measuring 30 to 50 mm) are relatively weak and not very durable. Because of these limitations, conventional nonwoven fabrics are mostly used in disposable market segments such as sanitary napkins, baby wipes, household wipes, fabric dryer sheets, and other industry-specific disposable applications. The efficiency through which nonwoven fabrics can be produced gives them an economic advantage over traditional woven or knitted fabrics in these types of disposable applications.

Nonwoven fabrics have been produced through hydroentanglement. Hydroentangled nonwoven fabrics are alternatively known in the art as “spunlace fabrics”, “spunlace” or “spunlaced.” Improvements have been made to these hydroentanglement processes to improve the properties of the nonwoven fabric with particular emphasis placed on the durability of the fabric and improved fabric integrity.

A more durable nonwoven fabric may be achieved by adding bonding agents to the fiber matrix. The fibers of nonwoven fabrics that have been reinforced through bonding have tended to result in fabrics that are often stiff. Further, reinforcement through the use of bonding agents generally results in the surfaces of the fabric having an undesirable tactile quality. Additionally, the nature of the unsmooth, bonded nonwoven fabric surfaces are less prone to adhering to pigments or inks, which limits the extent of additional treatments these fabrics may undergo.

Surface effects such as images or patterns have been imparted to nonwoven fabrics by calendaring the formed fabric through, for example, calendar embossing rollers. More recently, hydroentanglement techniques have also been developed to impart images or patterns to the entangled fabric by hydroentangling the fibers on three-dimensional image transfer devices. Images or patterns may be imparted to nonwoven fabrics for reasons of aesthetics and/or for purposes of imparting certain functionality to the nonwoven fabric.

There remains a need for nonwoven fabrics that have strength and durability allowing the fabrics to be, for instance, used as a re-usable shopping bags or other articles. An additional need is for nonwoven fabrics that substantially retain their desirable features after several washings without the use of binding agents. A further need is for processes that can produce high strength, durable nonwoven fabrics having desirable textile features that are both reliable and economical, and for the final product to be compostable or biodegradable. The compositions and methods disclosed herein address these and other needs.

SUMMARY

In accordance with the purposes of the disclosed materials, compounds, compositions, articles, and methods, as embodied and broadly described herein, the disclosed subject matter, in one aspect, relates to nonwoven fabrics and methods for preparing and using such nonwoven fabrics. In a further aspect, the disclosed subject matter relates to durable, compostable, and/or biodegradable nonwoven fabrics.

The disclosed subject matter, in certain aspects, relates to a nonwoven fabric comprising a needle punched and/or hydroentangled web of nonwoven staple fibers having a first fiber component comprising natural cellulosic fibers with fiber lengths less than about 26 mm. Also disclosed are articles, such as bags, comprising the nonwoven fabrics disclosed herein. In other aspects, disclosed are methods for preparing a nonwoven fabric that comprise needle punching and/or hydroentangling a web of nonwoven staple fibers to form an interlaced fibrous structure, wherein the web comprises a first fiber component comprising natural cellulosic fibers with fiber lengths less than about 26 mm.

In certain embodiments, the web of nonwoven staple fibers can comprise a blend of short (e.g., less than about 26 mm) and long (e.g., greater than about 30 mm) staple fibers. In other embodiments, the web of nonwoven staple fibers can comprise a blend of at least one fiber type that is a natural cellulosic fiber such as cotton, kenaf, hemp, flax, ramie, pineapple, coir, or any combination thereof. In some examples, the at least one natural cellulosic fiber type can have a concentration of more than about 50% by weight based on the total weight of the nonwoven fabric. Other fibers that can be part of the web include fibers that are a variation of the nonwoven staple fibers, such as PLA, PHA, natural fibers such as wool, man-made cellulosic fibers such as rayon, and polyamides, any bicomponent fiber, or any combination thereof.

In certain embodiments, when a thermoplastic fiber such as PLA or PHA are used, the web can be further subjected to thermal processes to bond or emboss the fabric. In other embodiments, the web can be subjected to a chemical or resin bonding process. In yet other embodiments, the web can be subjected to a thermal bonding process and a chemical or resin bonding process.

When the web is subjected to a resin bonding process, the resin can be at least one of an acrylic and a polyurethane resin. In other examples, the acrylic and/or polyurethane resin can have a concentration from about 3% to about 5% by weight based on the total weight of the web.

In an embodiment, a substantially compostable durable nonwoven fabric can comprise more than one web layer. The more than one web layer can be subjected to needle punching, hydroentangling, and at least one of chemical or resin bonding and thermal bonding. The multilayer durable nonwoven fabric can comprise a first web layer, a third web layer, and a second web layer disposed in between the first web layer and the third web layer. The first web layer and the third web layer can each comprise a splittable bicomponent staple fiber. The splittable bicomponent staple fiber can have a concentration of at least about 25% by weight based on the total weight of the fiber layer. The splittable bicomponent staple fiber can have a cross-section of at least one of side-by-side, sheath-core, tipped trilobal, islands-in-the-sea, segmented pie, and segmented ribbon as examples.

Another aspect disclosed herein provides methods for preparing a compostable or substantially compostable durable nonwoven fabric including the steps of producing a carded matrix of a fiber having a substantially uniform basis weight on a web, the fiber having at least one of a staple fiber and a filament; cross-lapping the carded matrix; subjecting the carded matrix to at least one of needle punching and hydroentangling to form an interlaced fibrous structure; and bonding the interlaced fibrous structure through at least one of thermal bonding and chemical or resin bonding to form a bonded fibrous structure.

In another embodiment, the method for preparing a durable nonwoven fabric can additionally comprise the step of at least one of hydroentangling and calendering the bonded fibrous structure to provide a desired surface effect to the fabric.

Additional advantages will be set forth in part in the description that follows, and in part will be obvious from the description, or may be learned by practice of the aspects described below. The advantages described below will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive.

BRIEF DESCRIPTION OF THE DRAWING

The accompanying FIGURE, which is incorporated in and constitutes a part of this specification, illustrates several aspects described below.

FIG. 1 is a flowchart of an embodiment of the invention showing the steps of an exemplary process for producing a nonwoven fabric.

DETAILED DESCRIPTION

The present invention now will be described more fully hereinafter with reference to the accompanying drawing, in which some, but not all embodiments of the inventions are shown. Preferred embodiments of the invention may be described, but this invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. The embodiments of the invention are not to be interpreted in any way as limiting the invention.

Many modifications and other embodiments of the invention set forth herein will come to mind to one skilled in the art to which this invention pertain having the benefit of the teachings presented in the descriptions herein and the associated drawings. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims.

Also, throughout this specification, various publications are referenced. The disclosures of these publications in their entireties are hereby incorporated by reference into this application in order to more fully describe the state of the art to which the disclosed matter pertains. The references disclosed are also individually and specifically incorporated by reference herein for the material contained in them that is discussed in the sentence in which the reference is relied upon.

Definitions

In this specification and in the claims that follow, reference will be made to a number of terms, which shall be defined to have the following meanings:

Throughout the description and claims of this specification the word “comprise” and other forms of the word, such as “comprising” and “comprises,” means including but not limited to, and is not intended to exclude, for example, other additives, components, integers, or steps.

As used in the description and claims, the singular forms “a”, “an”, and “the” include plural referents unless the context clearly indicates otherwise. For example, reference to “a fiber” includes a plurality of such fibers.

Ranges can be expressed herein as from “about” one particular value, and/or to “about” another particular value. When such a range is expressed, another aspect includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another aspect. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint. It is also understood that there are a number of values disclosed herein, and that each value is also herein disclosed as “about” that particular value in addition to the value itself.

Where a range of values is provided, it is understood that each intervening value, to the tenth of the unit of the lower limit unless the context clearly dictates otherwise, between the upper and lower limit of that range and any other stated or intervening value in that stated range, is encompassed. The upper and lower limits of these smaller ranges may independently be included in the smaller ranges, and are also encompassed, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included.

“Optional” or “optionally” means that the subsequently described event or circumstance can or cannot occur, and that the description includes instances where the event or circumstance occurs and instances where it does not.

As used herein, a “staple fiber” means a fiber of finite length. A staple fiber can be a natural fiber or a fiber cut from, for example, a filament.

As used herein, a “filament” refers to a fiber that is formed into a substantially continuous strand.

As used herein, a “nonwoven fabric” means a fabric having a structure of individual fibers or filaments that are interlaid but not necessarily in an identifiable manner as with knitted or woven fabrics.

As used herein, the terms “carding” or “carded web” refers to the process of opening and aligning staple fibers that are first applied in a bulky bat through combing or otherwise treating to produce a web of generally uniform basis weight.

As used herein, the term “cross-lapped” means to spread a loose fiber, for example a filament or yarn, in a back and forth direction that is roughly transverse to the direction of the web on which the fiber is laid with the individual laps partially overlapping each other such that they form an acute angle with each other.

As used herein, “needle punching” means to mechanically entangle a web of either non-bonded or loosely bounded fibers by passing barbed needles through the fiber web.

As used herein, the terms “hydroentangle” or “hydroentangling” refers to a process by which a high velocity water jet or even an air jet is forced through a web of fibers causing them to become randomly entangled. Hydroentanglement can also be used to impart images, patterns, or other surface effects to a nonwoven fabric by, for example, hydroentangling the fibers on a three-dimensional image transfer device such as that disclosed in U.S. Pat. No. 5,098,764 to Bassett et al. or a foraminous member such as that disclosed in U.S. Pat. No. 5,895,623 to Trokhan et al., both fully incorporated herein by reference for their teachings of hydroentanglement.

As used herein, the terms “calender” or “calendering” refers to a process for imparting surface effects onto fabrics or nonwoven webs. Without intending to be limiting, a fabric or nonwoven web can be calendered by passing the fabric or nonwoven web through two or more heavy rollers, sometimes heated, under high nip pressures.

It is understood that throughout this specification, the identifiers “first” and “second” are used solely to aid in distinguishing the various components and steps of the disclosed subject matter. The identifiers “first” and “second” are not intended to imply any particular order, amount, preference, or importance to the components or steps modified by these terms.

Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation. All terms, including technical and scientific terms, as used herein, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs unless a term has been otherwise defined. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning as commonly understood by a person having ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present disclosure. Such commonly used terms will not be interpreted in an idealized or overly formal sense unless the disclosure herein expressly so defines otherwise.

Materials

In one aspect, disclosed herein are improved nonwoven fabrics. The disclosed nonwoven fabrics comprise fibers locked into place by various mechanisms including, but not limited to, needle punching, hydroentanglement, and thermal and/or resin bonding. The nonwoven fabrics can optionally be subjected to additional post-processing techniques that conventional nonwoven fabrics would otherwise be unable to withstand. Further, the disclosed nonwoven fabrics can be subject to other processes like carding, cross-lapping, and calendering.

Further, nonwoven fabrics that are produced using staple length fibers have the tendency to abrade or pill if not sufficiently entangled or not appropriately bonded with resins or through thermal stabilization. The nonwoven fabrics disclosed herein avoid this effect by combining short staple fibers with longer ones and by, e.g., using high pressure water jets in hydroentangling that will tie down all or nearly all surface fibers. Furthermore, the nonwoven fabrics disclosed herein allow the fabric to be cut or sewn without demonstrating a significant tendency to pill in the cut or broken part of the fabric.

In certain embodiments, the short stable fibers of the disclosed nonwoven fabrics can have a length of less than about 26 mm, less than about 24 mm, less than about 22 mm, less than about 20 mm, less than about 18 mm, less than about 16 mm, less than about 14 mm, less than about 12 mm, less than about 10 mm, less than about 8 mm, less than about 6 mm, less than about 4 mm, or less than about 2 mm, where any of the stated values can form an upper or lower endpoint of a range. The short stable fibers can be at least about 0.5 mm, e.g., from about 0.5 mm to about 26 mm, from about 1 mm to about 26 mm, from about 5 mm to about 26 mm, from about 10 mm to about 26 mm, from about 10 mm to about 20 mm, from about 5 mm to about 20 mm, from about 0.5 mm to about 20 mm, or from about 0.5 mm to about 10 mm. In specific examples, the short staple fibers can be cellulosic fibers.

Further, the long fibers of the disclosed nonwoven fabrics can have a length of greater than about 30 mm, greater than about 50 mm, greater than about 1 cm, greater than about 5 cm, greater than about 10 cm, greater than about 50 cm, or greater than about 100 cm.

Without intending to be bound by theory, the nonwoven fabrics disclosed herein are characterized by having one or more improved physical properties such as, for example, grab tensile strength (e.g., ASTM D5034 that uses a tensile testing machine for measuring the highest tensile load achieved just before a fabric specimen tears or breaks), tongue tear strength (e.g., ASTM D2261 that uses a tensile strength test for measuring the force required to continue a rip through a prepared fabric specimen), air permeability (e.g., ASTM D737 for measuring the standard volume of air drawn through a fabric specimen of a defined area at constant temperature and pressure or the German test standard DIN 53 887 for measuring the quantity of air drawn through a fabric specimen at a fixed vacuum), moisture vapor transmission (e.g., ASTM E96 for measuring transfer of water vapor through a test fabric specimen over a fixed period of time), or any other test commonly used to measure a property related to the strength of a fabric. Such improvements can be realized in the longitudinal or machine direction, the transverse or cross machine direction, or both the longitudinal or machine direction and the transverse or cross machine direction.

In certain embodiments, the grab tensile strength in the machine direction of the nonwoven fabric can be at least about 30 lbs, at least about 50 lbs, at least about 100 lbs, at least about 120 lbs, at least about 140 lbs, at least about 160 lbs, at least about 180 lbs, at least about 190 lbs, or at least about 200 lbs, up to about 300 lbs. In other embodiments, the grab tensile strength in the cross machine direction of the nonwoven fabric can be at least about 30 lbs, at least about 50 lbs, at least about 80 lbs, at least about 90 lbs, at least about 100 lbs, at least about 110 lbs, at least about 120 lbs, at least about 130 lbs, or at least about 140 lbs, up to about 200 lbs. In still other embodiments, the tongue tear strength in the machine direction of the nonwoven fabric can be at least about 2.0 lbs, at least about 4.0 lbs, at least about 6.0 lbs, at least about 10.0 lbs, at least about 15.0 lbs, or at least about 20.0 lbs, up to about 30.0 lbs. In further embodiments, the tongue tear strength in the cross machine direction of the nonwoven fabric can be at least about 2.0 lbs, at least about 5.0 lbs, at least about 8.0 lbs, at least about 10.0 lbs, at least about 15.0 lbs, or at least about 20.0 lbs, up to about 30.0 lbs. Alternatively, the grab tensile strength and/or the tongue tear strength can be expressed as a ratio relative to the basis weight of the nonwoven fabric. Such ratios typically being expressed as either in the machine direction or the cross machine direction of the nonwoven fabric in units of lbs of force per grams per square meter or “gsm”.

In specific embodiments, the nonwoven fabrics disclosed herein can be specifically described in terms of durability of the fabric. The desired durability is typically established based on, among other things, the application where the fabric is intended to be used or the number of washes the fabric should be capable of sustaining. For example, in certain embodiments, the nonwoven fabric can be capable of sustaining at least 1 wash, at least 2 washes, at least 3 washes, at least 5 washes, at least 7 washes, at least 10 washes, at least 15 washes, at least 20 washes, at least 25 washes, at least 30 washes, at least 35 washes, at least 40 washes, at least 45 washes, or at least 50 washes under temperature, detergent solution, bleaching, and abrasive action conditions according to AATCC (American Association of Textile Chemists and Colorists) 61 wash test standard 2A for laundering.

Methods

Also disclosed herein are methods for the production of a nonwoven fabric. The disclosed methods can comprise any one or more of the following steps: producing a carded matrix of staple fibers, filaments, or combinations thereof having a substantially uniform basis weight on a precursor web; cross-lapping the carded matrix of staple fibers, filaments, or combinations thereof needle punching the carded and/or cross-lapped web of staple fibers, filaments, or combinations thereof entangling or interlacing the fibers, such as by hydroentanglement; bonding the fibers through a thermal bonding or resin bonding technique; and hydroentangling or calendaring the formed fabric to provide a desired surface effect to the fabric.

There are many combinations using any number of the steps of the disclosed methods as described herein for producing a nonwoven fabric. FIG. 1 is a flowchart illustrating a non-limiting exemplary embodiment of how some of the steps disclosed herein can be used to produce a nonwoven fabric. In this exemplary embodiment, a carded and/or cross-lapped web of fibers, for example staple fibers, can be subjected to needle punching, hydroentangling, or both needle punching and hydroentangling. Stitch-bonded fibers only subjected to needle punching can be bonded by at least one of resin bonding or thermal bonding. Entangled and interlaced fibrous structures can be directed to a calendering step for imparting texture and/or a surface effect on the nonwoven material. Alternatively, entangled and interlaced fibrous structures can be first bonded by at least one of resin bonding or thermal bonding and then subjected to a calendering step for imparting texture and or a surface effect on the nonwoven material. Fibers only subjected to needle punching will also preferably be subjected to a calendering step for imparting texture and/or a surface effect on the nonwoven material. Optionally, the nonwoven fabric can be subjected to post-treatment processes. Non-limiting examples of post-treatment processes include dyeing, printing, and combinations thereof.

A precursor web is formed embodying a carded fibrous matrix of staple fibers, filaments, yarns, or combinations thereof that has optionally also been cross-lapped. In certain embodiments, the precursor web can be formed only of a carded fibrous matrix. In other embodiments, the precursor web can be formed only of cross-lapped fibers.

Exemplary processes for producing a carded web include conventional air-laying processes known in the art such as those disclosed in U.S. Pat. No. 4,640,810 to Laursen et al. and U.S. Pat. No. 5,527,171 to Soerensen. In the air-laying processes, generally, a mat of fibers is fed down a chute into an air-laying apparatus that entrains the fibers into an airstream. Loose fibers fall from the airstream and are collected as a fibrous web material on a forming surface. Another type of carding process comprises the steps of disposing a mass of loose fiber on a supporting structure, repeatedly combing the disposed fibers with a multitude of needles, and repeating these steps until the desired thickness of a carded fibrous matrix is achieved. Any process for producing a carded web now known or later invented can be used in the inventive process for producing nonwoven fabrics. Any cross-lapping apparatus now know or later invented can be used to cross-lap the carded matrix of staple fibers, filaments, or combinations thereof.

In one aspect, the disclosed methods provide a nonwoven fabric. The nonwoven fabric can be formed from a single fiber type or a fiber blend. The nonwoven fabric can be described in terms of a first fiber component and a second fiber component. In certain embodiments, the first fiber component can comprise 100% by weight of the total fiber content of the nonwoven fabric. For example, while not intending to be limiting, the nonwoven fabric can be formed of a polyester fiber. In other embodiments, the nonwoven fabric can comprise the first fiber component and a certain content of a second fiber component. In other embodiments, the second fiber component can comprise one or more types of fibers. For example, while not intending to be limiting, the nonwoven fabric can be formed of a polyester/nylon fiber blend. Of course, reference to a first fiber component and a second fiber component does not limit the number of fiber components that can be used to prepare the nonwoven fabric. For example, when the nonwoven fabric is formed of a fiber component in addition to the first fiber component, the nonwoven fabric can be formed of two, three, or even more different types of fibers.

In certain embodiments, the nonwoven fabric comprises a first fiber component that is selected from at least one of a staple fiber, a filament, and combinations thereof. Preferably, the nonwoven fabric comprises a first fiber component that is a staple fiber. More preferably, the nonwoven fabric comprises a first fiber component that includes at least one fiber component comprising a polyester.

In a preferred embodiment, the nonwoven fabric is formed of a fiber blend comprising a first fiber component having high thermal stability. Preferably, the concentration of the first fiber component having high thermal stability is at least about 50% by weight of the total weight of the fibers. Yet even more preferably, the nonwoven fabric is formed of a fiber blend comprising a first fiber component having high thermal stability wherein the fiber having high thermal stability is the dominant fiber by weight based on the total weight of the fibers. In further embodiments, the first fiber component can comprise at least about 55% by weight, at least about 60% by weight, at least about 65% by weight, at least about 70% by weight, at least about 75% by weight, at least about 80% by weight, at least about 85% by weight, at least about 90% by weight, or at least about 55% by weight of the total weight of the fibers present in the inventive nonwoven fabric. Nonlimiting examples of materials that impart high thermal stability to fibers include man-made cellulosics such as rayon, natural cellulosic fibers such as cotton, hemp, Kenaf, Ramie, etc.

The second fiber component (or further fiber components) can be chosen from a variety of fiber types, including natural fibers, synthetic fibers, or a combination thereof. Other types of fibers that can be included in the nonwoven fabric include variations of the fibers as disclosed herein or blends of different fibers including, but not limited to, PLA, PHA, Rayon, Tencel, or any other bicomponent fiber. In a preferred embodiment, the nonwoven fabric includes a blend of PLA fibers and PHA fibers. More preferably, the concentration of PLA fibers will range from about 0.1 wt % to about 20 wt %, from about 0.5 wt % to about 50 wt %, or from about 1 wt % to about 90 wt % all based on the total weight of the fibers.

In certain embodiments, the disclosed nonwoven fabrics can comprise a second fiber component that includes a fiber with a melting point that is lower than the melting point of the first fiber component. Accordingly, the first fiber component and the second fiber component can be characterized in terms of their melting point (e.g., a first fiber component having a first melting point and a second fiber component having a second melting point that is less than the first melting point). Likewise, the nonwoven fabric can comprise a bicomponent fiber having a first component and a second component wherein the second component has a melting point that is lower than the melting point of the first component.

In yet other embodiments, the nonwoven fabric can include splittable fibers, such as splittable bicomponent fibers, that are designed to split into finer fibers as they are processed. Without intending to be limiting, uses for nonwoven fabrics having splittable fibers include wipes where smaller fibers are useful for picking up small pieces of dust, filtration, and insulation materials.

In other embodiments, the nonwoven fabric can comprise at least one multicomponent fiber. In a preferred embodiment, the multicomponent fiber is a bicomponent fiber. In yet another preferred embodiment, the multicomponent or bicomponent fiber has at least one component that is thermally stable as described herein. In another preferred embodiment, the multicomponent or bicomponent fiber has at least once component that is thermally stable that is the dominant component within the multicomponent or bicomponent fiber. For example, the thermally stable component will comprise the ‘island’ or the ‘core’ filaments respectively, while the ‘sea’ or ‘sheath’ component will enhance the bonding. Such embodiments can be an effective substitute for the binder fibers, e.g., PLA, of certain other embodiments of the invention.

Needle punching can be used to better interlock the carded and/or cross-lapped web of staple fibers, filaments, or combinations thereof. Needle punching can improve properties related to, for example, strength, absorption, and resistance to unraveling. The fibrous matrix is fed along a feed path into a needle loom. Any needling loom known in the art can be used in the disclosed methods such as, for example, a Dilo needle loom. A needle loom generally includes a reciprocally moving needle carrier for carrying a series of needles arranged in spaced rows or lines along the length of the carrier. The needle carrier is positioned such that when it is reciprocally engaged with the bed of the fibrous matrix structure, the barbs of the needles engage and pull fibers through the body of the fibrous matrix causing the engaged fibers to intertwine among other fibers within the carded and cross-lapped fibrous matrix. Without intending to be bound by theory, the interlocking that occurs causes the finished fabric to become generally more resistant to unraveling.

In one embodiment, the needle bed of the needle loom is substantially flat. In another embodiment, the needle bed of the needle loom is curved. In certain embodiments, a curved or an arcuate bed can be preferred since it increases the effectiveness of the interlocking that occurs in the fibrous matrix because the needles enter the fibrous matrix structure at varying angles.

Hydroentanglement further serves to entangle or interlace the fibers of the stitch-bonded fibrous structure. The fibers of the stitch-bonded fibrous structure can be interlaced by any hydroentanglement process known in the art. For example, one or more water jets under pressure can be directed at one or both sides of the base fibrous structure to cause the fibers to become entangled in a repeating pattern of localized entangled regions. The localized entangled regions can in turn become interconnected by fibers extending between adjacent entangled regions. In another exemplary process, hydroentanglement includes applying a jet of air to the nonwoven material to dry, cure, and/or bond the fibers of the nonwoven material. While not intending to be limiting, the dwell time, temperature and velocity of the air can be adjusted to achieve the desired degree of entanglement and/or bonding in the nonwoven fabric. An example of such a bonding system includes the rotary and the flatbed THRU-AIR™ Systems commercially available from the Honeycomb Division of Metso Paper (Helsinki, Finland).

Hydroentanglement causes the fibers to turn, wind, twist back-and-forth passing about one another in a random but intricate entanglement causing the fibers to become interlocked. Regions of fiber entanglement can extend substantially continuously along straight paths or can be distinct entangled masses of other appearances. Patterns having distinct regions of entangled fibers formed within the fibrous structure can be controlled by the apertures of the supporting web on which the fibrous structure is carried. Repeating patterns of distinct regions of fiber entanglement can be made to be regular wherein substantially identical arrangements are repeated periodically in at least one direction in the plane of the fabric, or the repeating pattern of distinct regions of fiber entanglement can be made to be irregular. A key to durability of the structure is that there are at least 3 manifolds with each having pressures in the range of 50 bar to 300 bar.

In an embodiment, the interlaced fibrous structure is bonded through a resin bonding technique wherein a sufficient amount of resin is added to the interlaced fibrous structure to achieve a desired strength in the fabric. Non-limiting examples of resins include acrylics, polyurethanes, latexes, and any combination thereof. In one embodiment, the resin is impregnated in the interlaced fibrous structure. In other embodiments, the resin is applied by passing the interlaced fibrous structure through a bath of the resin. In yet other embodiments, the interlaced fibrous structure is sprayed with the resin. Indeed, any process known in the art for applying resins can be used in the methods disclosed herein.

In certain embodiments, the resin is heated and cured to enhance the strength and the durability of the structure. Preferably, the amount of heat during curing will be sufficient to partially melt a secondary fiber and/or fiber component that has been included in the structure to cause additional bonding to occur within the fibrous structure.

In an embodiment, the functional groups of the resin, such as, for example, amine groups, epoxy groups, or any combination thereof, are selected to promote the type of bonding that is desired to be achieved in the interlaced fibrous structure. For example, in one embodiment, the functional groups of the resin are selected to promote bonding within the resin itself. In other embodiments, the functional groups of the resin are selected to promote bonding with one or more of the types of fibers included in the fibrous structure. In yet other embodiments, the functional groups of the resin are selected to promote bonding both within the resin itself and with one or more of the types of fibers included in the fibrous structure.

In certain embodiments, the concentration of resin bonding agent included in the nonwoven fabric is less than about 10% by weight of the total weight of the nonwoven fabric. In other embodiments, the concentration of bonding agent included in the nonwoven fabric is less than about 9%, about 8%, about 7%, about 6%, about 5%, about 4%, about 3%, about 2.5%, about 2%, about 1.5%, about 1%, or about 0.5% by weight of the total weight of the nonwoven fabric. In certain embodiments, the amount of resin applied to the interlaced fibrous structure is chosen based on the durability desired for the finished fabric. Fabric durability can be evaluated by the various means described herein.

Preferably, the resin will have at least one of an acrylic or polyurethane. More preferably, the resin having at least one of an acrylic or polyurethane will have a concentration from about 3% to about 5% by weight based on the total weight of the nonwoven fabric.

Optionally, an image, pattern, or other surface effect can be imparted to the nonwoven fabric. Techniques for imparting an image, pattern, or surface effect to the nonwoven fabric include hydroentanglement processes as already described herein and calendering. Indeed, any process known in the art for imparting an image, pattern, or surface effect to a web can be used in the disclosed methods.

While images, patterns, or other surface effects can be for aesthetic purposes, such processing techniques can also be used to influence other properties of the nonwoven fabric. For example, calendering the nonwoven can help to smooth the surface of the finished fabric. Calendering can also be useful in achieving a desired thickness of the nonwoven fabric when thickness is important for a particular application. As would be understood by a person having ordinary skill, when the thickness of a formed nonwoven fabric is reduced by a calendering process, the density of the fabric becomes increased. While helping to achieve a certain thickness, calendering can also be useful for eliminating variations in thickness of the nonwoven fabric.

Additionally, the mesh of the belt can be chosen not only to provide a desired texture to the inventive nonwoven fabric but also to affect the desired properties of the inventive nonwoven fabric. As used herein, the term “mesh count” refers to the number of openings per lineal inch of a mesh screen. The openings are delineated by strands, typically plastic threads or wires, in the mesh screen. Optionally, the mesh count can be selected to be substantially the same or different in the longitudinal or machine direction (MD) and the transverse or cross machine direction (CD). Non-limiting examples of properties of the inventive nonwoven fabric that can be affected by patterning imparted by, for example, a belt mesh include grab tensile strength, tongue tear strength, and any combination thereof in at least one direction MD and CD of the inventive nonwoven fabric. In an embodiment, the mesh size is less than about 100 mesh, less than about 50 mesh, less than about 40 mesh, less than about 30 mesh, less than about 25 mesh, and less than about 20 mesh. In a preferred embodiment, the mesh size is less than about 14 mesh. In another preferred embodiment, the mesh size is substantially equal to about 14 mesh. In yet another preferred embodiment, the mesh is a herringbone mesh screen. In another embodiment, the diameter of the strands of the mesh screen are selected to achieve a preferred property of the inventive nonwoven fabric, for example, any such property for the nonwoven fabric as disclosed herein.

In an embodiment, the basis weight, or the weight per unit surface area, of the nonwoven fabric will affect the properties of the nonwoven fabric. In an embodiment, the basis weight of the fabric will be at least about 50 grams per square meter (gsm), at least about 100 gsm, at least about 120 gsm, at least about 130 gsm, at least about 140 gsm, at least about 150 gsm, at least about 160 gsm, at least about 170 gsm, at least about 180 gsm, or at least about 200 gsm, up to about 500 gsm. Without intending to be limiting, generally, when all other factors are constant, increasing the basis weight of the nonwoven fabric will cause the strength or, more specifically, a property measurement related to the strength of the nonwoven fabric to become increased.

In an embodiment, the process for producing a nonwoven fabric comprises forming two or more layers of carded and/or cross-linked matrices of staple fibers, filaments, or combinations thereof. The fibers of each of the layers are at least one of needle punched, hydroentangled, interlaced, resin bonded, and thermal bonded. Each of the layers of the nonwoven fabric can also be subjected to at least one of needle punching, hydroentangling, resin bonding, and thermal bonding to form additional fiber-to-fiber bonds.

In another preferred embodiment, the nonwoven fabric comprises three layers of carded and/or cross-linked matrices of staple fibers as disclosed above, and at least one of the first layer and the third layer is a spunbonded splittable fiber web and the second layer, disposed between the first layer and the third layer, is a staple fiber web, or a web comprising a staple fiber. Preferably, this three-layer web is needle punched and/or hydroentangled, and subjected to at least one of resin bonding or thermal bonding to form additional fiber to fiber bonds.

Many variables, even beyond those processing variables as described herein, can impact the characteristics of the nonwoven product produced by the inventive process. Examples of variables that will be determinative of the type of nonwoven product that can be produced include, but are not limited to, the initial material or materials used in the formation of the fibrous web, types and amounts of staple fibers versus filaments used in the formation of the fibrous matrix structure, the patterning that occurs during the carding and cross-lapping steps, the nature and physical characteristics of the fibers used in the formation of the fibrous matrix structure, and the basis weight of the fabric.

In another embodiment, the disclosed nonwoven fabrics can include one or more additives. Such additives can include, for example, fire retardants, anti-static agents, antimicrobials, or any other type of additive commonly used in fabrics for personal and commercial use. In an embodiment, the additives can be included in the fibers of the fiber matrix. In another embodiment, the additives can be included in at least one of the fiber types of a fiber blend. In yet another embodiment, the additive can be disposed substantially at the surface of the fibers of the fiber matrix or the surface of at least one of the fiber types of a fiber blend.

The invention also provides a number of products of manufacture that can be made using the nonwoven fabrics as described herein. Applications where the inventive fabrics can be useful include, but are not limited to, any application where the durability of the inventive nonwoven fabrics is desirable. Such applications include, but are not limited to, clothing or other fabrics where multiple laundering is desired and fabrics where nonwoven materials have traditionally been used.

Examples

The effect of varying ratios of blended Cotton and Polylactic acid (PLA) fibers, varying amounts and types of binder, varying fabric basis weights and several different patterns in finished nonwoven fabrics on the grab tensile strength and the tongue tear strength were measured. Grab tensile strength is a measure of the breaking strength of the fabric and can be measured by the method provided in ASTM D5034. According to ASTM D5034, the fabric sample is placed into a tensile testing machine that grips the fabric with two clamps, and one clamp slowly moves away from the other clamp, which remains stationary. The grab tensile strength is the highest tensile load achieved just before the fabric tears or breaks. Grab tensile strength can be measured in the machine direction and the cross machine direction of the fabric.

Tongue tear strength is a measure of the force required to continue a rip through the fabric and can be measured by the method provided in ASTM D2261. According to ASTM D2261, a rectangular piece of fabric of specific dimensions is slit in the center approximately half-way down the short direction of the fabric. The two ends of the slit piece are subjected to a tensile strength test. The tongue tear strength is the highest tensile load achieved just before the fabric begins to tear or break. Tongue tear strength can be measured in the machine direction and the cross machine direction of the fabric.

Examples

A set of nonwoven fabric was prepared with 100 wt % Cotton fibers. Additionally, three sets of nonwoven fabrics were prepared with varying ratios of Cotton to PLA fibers—75/25, 50/50, and 25/75 (Examples 2-4, respectively).

The PLA fibers measure 25 mm in length.

Each of the nonwoven fabrics had a fabric basis weight of 100, 150, and 200 g/m² (gsm), and were patterned with a 100 mesh screen as disclosed herein using a hydroentangling belt. The fabrics were subjected to 5 manifolds with pressures set as: 30, 50, 100, 150 and 220 bar.

The total number of samples were 12 and details are shown in Table 1.

TABLE 1 Cotton/PLA (%) 25/75 50/50 75/25 100/0 Weights (g/m²) 100, 150, 200

Each of the nonwoven fabric samples were tested for weight, thickness, burst strength, and air permeability according to the test standards noted herein. The results for weight and thickness are shown in Table 2.

TABLE 2 Actual Air Target Weight Cotton/PLA Weight Thickness Permeability Ball Burst (g/m²) (%) (g/m²) (μm) (ft³/ft²/min) (lbf) 200 25/75 192 ± 1.8 1127 ± 7.5  78.96 ± 2.1 98.2 ± 1.6 50/50 206 ± 2.1 1125 ± 7.1  45.08 ± 1.4 92.8 ± 1.4 75/20 211 ± 1.8 1060 ± 8.4  33.94 ± 0.7 80.9 ± 2.1 100/0  207 ± 3.0 1011 ± 9.2  30.04 ± 1.0 70.0 ± 2.0 150 25/75 147 ± 1.3 934 ± 6.9  105.58 ± 2.2  74.5 ± 1.8 50/50 156 ± 1.8 936 ± 9.8  69.98 ± 1.4 64.8 ± 1.1 75/20 152 ± 4.0 849 ± 6.6   54.7 ± 2.7 50.2 ± 1.5 100/0  141 ± 2.5 814 ± 7.1    52 ± 2.1 41.1 ± 1.7 100 25/75 104 ± 3.1 741 ± 12.6 149.2 ± 6.4 47.2 ± 3.5 50/50 104 ± 2.9 741 ± 12.4 128.8 ± 6.4 40.1 ± 2.2 75/20  95 ± 1.7 692 ± 10.7 116.2 ± 4.0 30.0 ± 1.1 100/0   97 ± 4.1 668 ± 13.2   92 ± 5.6 30.1 ± 2.2

Interestingly, the addition of PLA improves the performance. The addition of PLA improves the burst strength but also results in higher air permeability and a slightly bulkier structure. The higher percentage of cotton results in lower thickness, lower air permeability and higher consolidation.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims. 

What is claimed is:
 1. A nonwoven fabric, comprising: a needle punched and/or hydroentangled web of nonwoven staple fibers having a first fiber component comprising natural cellulosic fibers with fiber lengths less than about 26 mm.
 2. The nonwoven fabric of claim 1, wherein the web further comprises a second fiber component comprising fiber lengths greater than about 30 mm.
 3. The nonwoven fabric of claim 2, wherein the second fiber component is selected from the group consisting of PLA, PHA, a man-made cellulosic fiber, a bicomponent fiber, and any combination thereof.
 4. The nonwoven fabric of claim 1, wherein the natural cellulosic fibers are more than about 50% by weight based on the total weight of the nonwoven fabric.
 5. The nonwoven fabric of claim 1, wherein the web is needle punched and/or hydroentangled at high pressure to reach an air permeability of 150 cfm or less and a bursting strength of 30 pounds or higher, at a weight of at least 100 g/m².
 6. The nonwoven fabric of claim 1, wherein the natural cellulosic fibers are selected from the group consisting of cotton, kenaf, hemp, flax, ramie, pineapple, coir, and any combination thereof.
 7. The nonwoven fabric of claim 1, further comprising an acrylic or a polyurethane resin at from about 1% to about 15% by weight based on the total weight of the nonwoven fabric.
 8. The nonwoven fabric of claim 1, wherein the fabric comprises one or more additional webs of nonwoven staple fibers.
 9. The nonwoven fabric of claim 1, wherein the nonwoven fabric comprises a first web layer, a third web layer, and a second web layer disposed between the first web layer and the third web layer, wherein the web layers are needle punched and/or hydroentangled, and at least one of the web layers is thermally bonded and chemically bonded.
 10. The nonwoven fabric of claim 9, wherein each of the first web layer and the third web layer comprises a splittable bicomponent staple fiber such that the entire content of the splittable bicomponent staple fiber comprises from about 25% to about 50% by weight of the total weight of the nonwoven fabric.
 11. The nonwoven fabric of claim 10, wherein the splittable bicomponent staple fiber has a cross-section selected from the group consisting of side-by-side, tipped trilobal, segmented pie, segmented ribbon, islands in the sea, and any combination thereof.
 12. The nonwoven fabric of claim 9, wherein each of the first web layer and the third web layer is a spunbonded web comprising a splittable bicomponent fiber and the second web layer comprises a staple fiber bonded together mechanically by needle punching and/or hydroentangling.
 13. The nonwoven fabric of claim 12, wherein the splittable bicomponent fiber comprises from about 25% to about 50% by weight of the total weight of the fibers comprising the spunbonded web.
 14. The nonwoven fabric of claim 12, wherein at least a portion of the splittable bicomponent fibers of the spunbonded web are partially split and are entangled with at least a portion of the staple fibers of the second web layer.
 15. A bag comprising the nonwoven fabric of claim
 1. 16. A method for preparing a nonwoven fabric, comprising: needle punching and/or hydroentangling a web of nonwoven staple fibers to form an interlaced fibrous structure, wherein the web comprises a first fiber component comprising natural cellulosic fibers with fiber lengths less than about 26 mm.
 17. The method of claim 16, wherein before needle punching and/or hydroentangling the web of nonwoven staple fibers is prepared by producing a carded matrix of a fiber on a web, the fiber having a substantially uniform basis weight; and cross-lapping the carded matrix.
 18. The method of claim 16, further comprising bonding the interlaced fibrous structure to form a bonded fibrous structure.
 19. The method of claim 16, further comprising hydroentangling and calendering the bonded fibrous structure to provide a surface effect to the fabric.
 20. The method of claim 16, wherein bonding the interlaced fibrous structure comprises thermally bonding and/or chemically bonding.
 21. The method of claim 16, wherein the web comprises a second fiber component, the second fiber component being selected from the group consisting of PLA, PHA, a man-made cellulosic fiber, a bicomponent fiber, and any combination thereof.
 22. The method of claim 16, wherein the web is needle punched and/or hydroentangled at high pressure to reach an air permeability of 150 cfm or less and a bursting strength of 30 pounds or higher, at a weight of at least 100 g/m².
 23. The method of claim 16, wherein the natural cellulosic fibers are selected from the group consisting of cotton, kenaf, hemp, flax, ramie, pineapple, coir, and any combination thereof. 